diff --git a/src/corelib/kernel/qmetaobjectbuilder.cpp b/src/corelib/kernel/qmetaobjectbuilder.cpp
index 5dd86d4b0e4..a2719f97da7 100644
--- a/src/corelib/kernel/qmetaobjectbuilder.cpp
+++ b/src/corelib/kernel/qmetaobjectbuilder.cpp
@@ -1649,6 +1649,7 @@ QList<QByteArray> QMetaMethodBuilder::parameterNames() const
 void QMetaMethodBuilder::setParameterNames(const QList<QByteArray> &value)
 {
     QMetaMethodBuilderPrivate *d = d_func();
+    Q_ASSERT(d->parameterCount() >= value.size());
     if (d)
         d->parameterNames = value;
 }
diff --git a/tests/auto/corelib/kernel/qmetaobjectbuilder/tst_qmetaobjectbuilder.cpp b/tests/auto/corelib/kernel/qmetaobjectbuilder/tst_qmetaobjectbuilder.cpp
index fc48111e296..7c0e5e10b71 100644
--- a/tests/auto/corelib/kernel/qmetaobjectbuilder/tst_qmetaobjectbuilder.cpp
+++ b/tests/auto/corelib/kernel/qmetaobjectbuilder/tst_qmetaobjectbuilder.cpp
@@ -45,6 +45,8 @@ private slots:
 
     void ownMetaTypeNoProperties();
 
+    // void tooLongParameterNamesList(); // QTBUG-139845
+
 private:
     static bool checkForSideEffects
         (const QMetaObjectBuilder& builder,
@@ -1770,6 +1772,36 @@ void tst_QMetaObjectBuilder::enumCloning()
     }
 }
 
+// Can't use this unittest on the CI because it hits an assert
+// void tst_QMetaObjectBuilder::tooLongParameterNamesList()
+// {
+//     // QTBUG-139845
+//     QMetaObjectBuilder builder;
+//
+//     builder.setSuperClass(&QObject::staticMetaObject);
+//
+//     QMetaMethodBuilder methodBuilder = builder.addSignal("iChanged(int)");
+//     methodBuilder.setParameterNames({"i"});
+//     int icIdx = methodBuilder.index();
+//
+//     methodBuilder = builder.addSignal("fChanged(float)");
+//     methodBuilder.setParameterNames({"f"});
+//     int fcIdx = methodBuilder.index();
+//
+//     methodBuilder = builder.addSlot("pushI(int)");
+//     methodBuilder.setParameterNames({"i"});
+//     builder.addSlot("reset()");
+//     methodBuilder = builder.addSlot("add(int)");
+//     methodBuilder.setParameterNames({"", "i"});
+//
+//     methodBuilder.setReturnType("int");
+//
+//     builder.addProperty("i", "int", icIdx);
+//     builder.addProperty("f", "float", fcIdx);
+//
+//     builder.toMetaObject();
+// }
+
 void tst_QMetaObjectBuilder::ownMetaTypeNoProperties()
 {
     QMetaObjectBuilder builder;